Synthesis and characterisation of new Schiff base metal complexes and their use as catalysts for olefin cyclopropanation

Article abstract of DOI:10.1016/j.ica.2008.09.012

New transition metal complexes of Co^II, Cu^II, Ni^II and V^IVO with the Schiff base, HL, 3-acetylcoumarin-N(4)-phenylthiosemicarbazone have been prepared. Characterisation of the HL ligand and its complexes is also

Full text of DOI:10.1016/j.ica.2008.09.012

Inorganica Chimica Acta 362 (2009) 2006–2014
Contents lists available at ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Synthesis and characterisation of new Schiff base metal complexes
and their use as catalysts for olefin cyclopropanation
a
a
b,
Nabil S. Youssef a, , Eman El-Zahany , Ahmed M.A. El-Seidy , Alessandro Caselli
,
*
*
Simone Fantauzzi b, Sergio Cenini b
a Inorganic Chemistry Department, National Research Centre, Dokki, Giza, Egypt
b Dipartimento di Chimica Inorganica, Metallorganica e Analitica ‘‘Lamberto Malatesta”, Università degli Studi di Milano, and ISTM-CNR;Via Venezian 21, 20133 Milan, Italy
a r t i c l e i n f o
a b s t r a c t
New transition metal complexes of CoII, CuII, NiII and VIVO with the Schiff base, HL, 3-acetylcoumarin-
N(4)-phenylthiosemicarbazone have been prepared. Characterisation of the HL ligand and its complexes
is also reported. Mass spectra and NMR assignments for the ligand, using COSY, NOESY homonuclear and
HMQC and HMBC heteronuclear correlation techniques were carried out. Electronic and magnetic
moments of the complexes indicate that the geometries of the metal centres are either distorted octahe-
dral, square pyramidal, square planar or tetrahedral. The structures are consistent with the IR, UV–Vis,
ESR, as well as conductivity and magnetic moments measurements. Cyclopropanation reactions of unac-
tivated olefins by ethyldiazoacetate (EDA) in the presence of LCuIICl as catalyst proceed with excellent
TON (up to 9625).
Article history:
Received 6 May 2008
Received in revised form 3 September 2008
Accepted 10 September 2008
Available online 16 September 2008
Keywords:
Schiff bases
Metal complexes
Cyclopropanation
Homogeneus catalysis
Ó 2008 Elsevier B.V. All rights reserved.
1. Introduction
today, the cycloaddition of carbenoids to C@C double bonds is
practically the most important one to construct this class of com-
In the recent years, considerable attention has been given to the
preparation of transition metal complexes of Schiff bases due to
their interesting and important properties. Schiff bases represent
a class of important compounds in medicinal and pharmaceutical
field. They have biological activities such as antibacterial [1–4],
anticancer [5–7], antifungal [8,9] and herbicidal activities [10]. Fur-
thermore, Schiff bases offer opportunities for inducing substrate
chirality, tuning metal centred electronic factors, enhancing solu-
bility and stability of either homogeneous or heterogeneous cata-
lyst [11–16]. For instance there are several studies on Schiff base
copper(II) and cobalt(II) complexes used for asymmetric and enan-
tioselective catalysis [17–24]. Based on the aforementioned prop-
erties for Schiff bases and their complexes, we report herein the
synthesis and spectroscopic studies of the Schiff base ligand HL,
3-acetylcoumarin-N(4)-phenylthiosemicarbazone, (1) and its CoII,
CuII, NiII and VIVO complexes. 13C NMR spectra were also obtained
to determine the structure of the ligand. The catalytic activity of
complexes [L2Co2Cl2] ꢀ 2H2O (2), [LCo(OC(O)CH3)] ꢀ H2O (3) and
LCuIICl (5) toward the decomposition of ethyl diazoacetate (EDA)
in the presence of olefins to yield cyclopropane products has also
been investigated. Although various methodologies are available
pounds. Stereochemical control of these reactions, such as differen-
tiation of the enantiotopic faces of the double bond or cis–trans
selectivity imposed on the cyclopropanation reaction by the pres-
ence of a substituent at the carbenoid carbon are the main issues
[25,26]. However, another issue of the cyclopropanation is the che-
moselectivity of the reaction: very often catalysts that are fast in
the activation of the approaching carbenoid, namely diazoacetates,
give olefins derived by coupling reactions as major by products.
Rarely metal complexes can give high selectivities in cyclopropa-
nation reactions together with high turnover number (TON). We
report here that LCuIICl (5) is a competent catalyst for the cyclo-
propanation of olefins.
2. Experimental
2.1. Material
All the reagents employed for the preparation of the ligand and
its complexes were of the best grade available and used without
further purification. Unless otherwise stated, all catalytic tests
were carried out under an atmosphere of purified dinitrogen using
modified Schlenk techniques. Solvents employed were dried and
distilled before use by standard methods. Benzene, cyclohexene
and 1-octene were distilled over sodium, styrene and
styrene were distilled over calcium hydride and stored under
dinitrogen.
a-methyl
* Corresponding authors. Tel.: +39 02 5031 4372; fax: +39 02 5031 4405.
E-mail addresses: nabilyoussef@hotmail.com (N.S. Youssef), alessandro.caselli@
unimi.it (A. Caselli).
0020-1693/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2008.09.012

N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
2007
H
N
H
N
NCS
H2NNH2·H2O
H2N
+
S
N(4)-phenylthiosmicarbazide
H
N
H
N
H2N
O
Acetic acid (pH=5.5)
reflux
+
S
O
O
O
O
O
O
S
SH
N
N
N
H
N
H
N
N
H
Scheme 1. Schematic representation for the formation of the Schiff base ligand HL (1).
H7'
H6'
H6
H7'
H6'
H6
CH3 H1 H2
CH3 H1 H2
H
H
H
H8
N
N
H3
H4
H8
N
N
H3
H4
N
N
H7
H7
17
S
SH
O
O
O
O
H5
H5
CH3
21' 20'
H
H
N
19
12
4
10
7
22
N
15
3
2
5
9
N
13
18
14
21 20
6
8
S
16
O
O
1
11
Chart 1. Numbering scheme for ligand HL (1).
2.2. Synthesis of the Schiff base ligand HL
C(18), 135.3 C(8), 131.6 C(10), 129.8 C(21) and C(210), 125.8 C(9),
121.8 C(22), 117.6 C(20) and C(200), 117.0 C(7) and 30.9 C(17).
The Schiff base ligand HL (1) was prepared in two steps. The
reactions steps are illustrated in Scheme 1 (see Chart 1).
2.3. Synthesis of the metal complexes
2.2.1. Synthesis of the N(4)-phenylthiosemicarbazide
The metal complexes of the ligand HL (1) were prepared by
N(4)-phenylthiosemicarbazide is prepared as reported in the lit-
erature. A solution of hydrazine hydrate (0.370 g, 7.397 mmol) in
methanol (10 ml) was added dropwise to a stirred solution of
phenylisothiocyanate (1.000 g, 7.397 mmol) in methanol (10 ml)
at room temperature. A white precipitate starts to form immedi-
ately upon addition, the stirring was continued for 30 min, after
which the white solid was filtered, washed with methanol and
dried under vacuum over anhydrous CaCl2 (97% yield).
mixing a hot methanolic solution of the metal chlorides:
CoCl2 ꢀ 6H2O, CuCl2 ꢀ 2H2O, NiCl2 ꢀ 6H2O, metal acetates: Co(CH3-
COO)2 ꢀ 4H2O, Ni(CH3COO)2 ꢀ 4H2O, Cu(NO3)2 or VOSO4 ꢀ H2O with
the required amount of a hot ethanolic solution of the ligand to
form 1:1 or 1:2 M/L (metal/ligand) complexes, or in the presence
of 1,10-phenanthroline (Phen) as a secondary ligand, as shown in
Table 1. The reaction mixture was then refluxed for a time depend-
ing on the transition metal salt used. Some complexes: 2, 6 and 9
did not separate on standing but only when an aqueous KOH solu-
tion (0.5 mol ꢁ dmꢂ3) was added under stirring until the pH
reached ꢃ5.0. Formation of all complexes began with a change in
the colour of the mixture. In the case of complex 5 instead of add-
ing KOH solution, the solution was concentrated to half of its origi-
nal volume before the formation of a green precipitate was
observed. The precipitates formed were filtered, washed with eth-
anol, then with diethyl ether and dried under vacuum over anhy-
drous CaCl2.
2.2.2. Synthesis of the ligand, HL (1)
A few drops of glacial acidic acid were added to a hot solution
(75 °C) of 3-acetyl-2H-chromen-2-one (1.125 g, 5.980 mmol) in
ethanol (20 ml) and the mixture was then added to a hot solution
(75 °C) of N(4)-phenylthiosemicarbazide (1.000 g, 5.980 mmol) in
dioxane (10 ml). The reaction mixture was refluxed for 15 h. After
cooling, water was added and a yellow precipitate started to form;
the solid was filtered and washed with water then with ethanol.
The product was re-crystallised from ethanol and dried under vac-
uum over anhydrous CaCl2 (75% yield). 1H NMR (300 MHz, DMSO):
2.4. Physical measurements
d = 9.83 (s, 1H, NH), 8.66 (s, 1H, H1), 7.96 (d, J = 8.4 Hz, 1H, H2), 7.76
0
(pst, J = 8.4 Hz, 1H, H4), 7.55 (d, J = 7.5 Hz, 2H, H6, H6 ), 7.47 (d,
The ligand and its metal complexes were analysed for C, H, N and
M contents at the Microanalytical Laboratory, Faculty of Science,
Cairo University, Egypt. Analytical and physical data of the ligand
HL and its metal complexes are reported in Table 2. The metal ion
contents of the complexes were also determined [27–29] by the
J = 8.4 Hz, 1H, H5), 7.43 (pst, J = 8.4 Hz, 1H, H3), 7.30 (pst,
0
J = 7.5 Hz, 2H, H7, H7 ), 6.94 (t, J = 7.5 Hz, 1H, H8), 3.31 (s, SH) over-
lapping with H2O, 2059 (s, 3H, CH3). 13C NMR (300 MHz, DMSO,
300 K): 196.0 C(3), 159.0 C(12), 155.5 C(6), 147.9 C(4), 141.0

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N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
Table 1
Amounts of the reactants used in the formation of the metal complexes
No. Complex
Metal salt used
Metal chloride, nitrate, acetate, or sulphate HL ligand in 10–25 mL
Phenanthroline (Phen) in 20 mL
ethanol
in
ethanol
10–20 mL methanol
Mass (g)
mmol
Mass (g)
mmol
Mass (g)
mmol
1:1 M/L
2
3
4
5
6
10
[L2Co2Cl2] ꢀ 2H2O
CoCl2 ꢀ 6H2O
0.476
2.0
2.0
2.0
2.5
2.5
2.0
0.676
0.676
0.675
0.843
0.843
0.675
2.0
2.0
2.0
2.5
2.5
2.0
[LCo(OC(O)CH3)] ꢀ H2O
Co(CH3COO)2 ꢀ 4H2O 0.499
[LVO(H2O)]2ꢀ(SO4) ꢀ H2O VO(SO4) ꢀ H2O
0.361
0.426
0.426
LCuCl
CuCl2 ꢀ 2H2O
CuCl2 ꢀ 2H2O
L2Cu2Cl2(H2O)2
LNi(OOCCH3)
Ni(CH3COO)2 ꢀ 4H2O 0.498
1:2 M/L
7
9
[L2Cu] ꢀ H2O
Cu(NO3)2 ꢀ 3H2O
NiCl2 ꢀ 6H2O
0.256
0.316
1.5
1.3
1.013
0.897
3.0
2.7
[L2Ni] ꢀ 3H2O
1:1:1 M/L/Phen
8
[LCuCl(Phen)]ꢀ2H2O
CuCl2 ꢀ 2H2O
0.512
3.0
1.013
3.0
0.541
3.0
Table 2
Analytical and physical data of the ligand HL and its metal complexes
No. Ligand/complexes
Colour
FW
Yield (%) Anal./found (calc.) (%)
Molar conductance Km (X )
ꢂ1 cm2 molꢂ1
C
H
N
M
1
2
3
4
5
6
7
8
9
10
HL
yellow
sap green 897.58 70
brown
337.40 65
63.95 (64.08) 4.60 (4.48) 12.65 (12.45)
48.19 (48.17) 3.73 (3.59) 9.55 (9.36)
50.70 (50.85) 4.02 (4.05) 8.76 (8.90)
44.99 (45.19) 3.50 (3.58) 8.63 (8.78)
49.49 (49.66) 3.12 (3.24) 9.51 (9.65)
47.86 (47.68) 3.33 (3.56) 9.19 (9.27)
57.14 (57.32) 4.01 (4.01) 11.31 (11.14) 8.28 (8.42)
55.14 (55.30) 4.22 (4.02) 10.57 (10.75) 9.59 (9.75)
55.05 (55.04) 4.22 (4.36) 10.98 (10.70) 7.34 (7.47)
[L2Co2Cl2] ꢀ 2H2O
13.00 (13.13) 13
12.33 (12.48) 15
10.57 (10.65) 110
14.45 (14.60) 11
14.18 (14.02) 10
[LCo(OC(O)CH3)] ꢀ H2O
472.38 84
478.38 67
435.39 94
903.98 76
753.10 82
650.07 72
785.51 80
454.12 81
[LVO(H2O)]2 ꢀ (SO4) ꢀ H2O green
LCuCl
green
brown
brown
brown
beige
L2Cu2Cl2(H2O)2
[L2Cu] ꢀ H2O
10
14
8
[LCuCl(Phen)] ꢀ 2H2O
[L2Ni] ꢀ 3H2O
LNi(OOCCH3)
ochre
52.64 (52.90) 3.73 (3.77) 9.36 (9.25)
12.67 (12.92) 17
previously reported methods [30,31]. IR spectra of the ligands and
their metal complexes were measured using KBr discs with a Jasco
FT/IR 300E Fourier transform infrared spectrophotometer covering
the range 400–4000 cmꢂ1 and in the 500–100 cmꢂ1 region using
polyethylene-sandwiched Nujol mulls on a Perkin Elmer FT-IR
1650 spectrophotometer. 1H and 13C NMR spectra were obtained
on Brucker Avance 300-DRX or Avance 400-DRX spectrometers.
Chemical shifts (ppm) are reported relative to TMS. The mass spectra
were run at 70 eV with HP MODEL: MS. 5988A and/or GCMS. Cap
1000 EX SHIMADZU spectrometer using Electron Impact Technique.
The electronic spectra of the ligands and their complexes were ob-
tained inNujolmulls andinsaturatedDMSOsolutions usinga Shima-
dzu UV–240 UV–Vis recording spectrophotometer. Molar
conductivities of the metal complexes in DMSO (10ꢂ3 M) were mea-
sured using a dip cell and a Bibby conductimeter MC1 at room tem-
perature. The resistance measured in ohms and the molar
conductivities were calculated according to the equation:
fin (see caption of Tables 6 and 7 for quantities) in 1,2-dichloroeth-
ane (10 mL). The resulting pale green solution was heated at the
required temperature under stirring; depending on the olefin used
and its concentration, after few minutes the solution turned to col-
ourless and dinitrogen started to evolve from the system. The reac-
tion was followed until total consumption of the EDA (IR
absorbance,
m
max = 2114 cmꢂ1, <0.025) was observed. The final
solution was analysed by GC–MS after the addition of 2,4-dinitro-
toluene as internal standard or evaporated to dryness under vac-
uum and products were separated by flash chromatography
(eluant n-hexane/ethylacetate).
3. Results and discussion
3.1. Mass spectra of the ligand
The mass spectra of the Schiff base ligand HL (1) revealed the
molecular ion peak at m/e 337, which is coincident with the for-
mula weight (337.4) for this ligand and supports the identity of
the structure. The pathway fragmentation pattern of the mass
spectrum of the ligand is depicted in Scheme 2.
K
= V ꢁ K ꢁ Mw/g ꢁ
X, where K
, molar conductivity (ohmꢂ1 cm2
molꢂ1); V, volume of the complex solution (mL); K, cell constant
0.92 cmꢂ1; Mw, molecular weight of the complex; g, weight of the
complex; and
X, resistance measured in ohms. Magnetic moments
at 298 K were determined using the Gouy method with Hg[Co(SCN)4]
as calibrant. The solid ESR spectra of the complexes were recorded
with ELEXSYS E500 Brucker spectrometer in 3-mm Pyrex Tubes at
298 K. Diphenylpicrylhydrazide (DPPH) was used as a g-marker for
the calibration of the spectra. Mass spectra of the solid ligand were
recorded using JEUL JMS-AX-500 mass spectrometer.
3.2. Infrared spectra of the complexes
IR spectra of the complexes were recorded to confirm their
structures. The most characteristic vibrational frequencies and
their tentative assignments for the ligand HL (1) and its transition
metal complexes are listed in Table 3. The assignments were
made by comparison with the vibrational frequencies of the free
ligand.
2.5. Typical procedure for the catalytic cyclopropanation of olefins by
LCuIICl (5)
The IR data obtained suggested that the ligand behaves as a
mononegative tridentate ligand and coordinates through the
C@N, C@O and C–S groups with displacement of one hydrogen
EDA (see caption of Tables 6 and 7 for quantities) was added to
a suspension of LCuIICl (5) (5.0 mg, 1.15 ꢁ 10ꢂ2 mmol) and the ole-

N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
2009
CH3
H
N
H
N
CH3
-N
N
172
C
S
N
C6H5
O
O
O
O
a
m/e186
C18H15N3O2S
337
C6H5-NH-CS NH
m/e151
H
CH3
-CH3
N
CS
m/e
322
N
O
O
m/e245
H
N
CH3
O
C6H5NH
92
C6H5-NH CS
m/e
136
N
O
m/e201
-NH
-NHCS
m/e59
C6H5 -CNS
m/e135
a
m/e186
-CH3CN
C6H5
m/e77
O
O
m/e145
Scheme 2. Fragmentation pattern of the ligand HL (1).
Table 3
IR frequencies of the bands (cmꢂ1) of ligand HL (1) and its complexes and their assignments
No. Compound
m(OH/H2O)
m
(N4H) (N2H)
m
m
(C@O)
m
(C@S)
m(C@N)
m
(N–N)
m(COO), s, as,
D
t
m(M–N)
m(M–S)
m(M–O)
1
2
3
4
5
6
7
8
9
10
HL
3241 b
3283 s
3197 m 1728 vs
1717 m
871 s
1605 s
1600 m1620 m
1116 s
1122 m
[L2Co2Cl2] ꢀ 2H2O
3411 br
3380 (br)
456 w
390 w
527 m
497 w
530 m
505 w
510 w
505 w
505 w
[LCo(OC(O)CH3)] ꢀ H2O
3295 w
3244 m
3270 sh
3287 m
3290 sh
3248 m
3212 w
3272 sh
1710 vw
1715 vw
1710 w
1720 vw
1714 m
1713 m
1738 m
1719 w
1598 m 1650 w 1155 m
1605vw1625 m 1146 sh
1602 w1628 vw 1122 w
1648 m1599 m
1606 w1620 m
1550vw1614 m
1603w1659 m
1600 m1654 m
1558, 1315,
Dt = 243 450 vw 355w
[LVO(H2O)]2ꢀ(SO4) ꢀ H2O 3401 br
460 m
422 w
445 w
450 w
467 w
455w
395 m
350w
340w
345w
380 w
LCuCl
3426 br
3435 br
3416 w
3420 br
3436 br
3421 br
L2Cu2Cl2(H2O)2
[L2Cu] ꢀ H2O
1120 w
1134 w
1133 m
1122 m
1132 w
[LCuCl(Phen)] ꢀ 2H2O
[L2Ni] ꢀ 3H2O
LNi(OOCCH3)
366 vw 486 w
370w 493 w
1532, 1435
D
t
= 97
451 w
atom upon enothiolization. In these complexes, the mode of
coordination was suggested by the following evidences: (i) the
group in a monodentate fashion [35]. The difference between the
1532 and 1435 cmꢂ1 = 97 cmꢂ1) bands is correlated to the
bidentate behaviour [36] in complex 10 (see Table 4).
(Dm
disappearance of
quency together with its weak appearance (iii) the presence of
a new band attributed to (C@N) [32] in the same spectral re-
gion for the (C@N) of the thiosemicarbazone moiety, (iv) the
shift of (N–N)
(C@O) by 8–18 cmꢂ1, (v) the occurrence of the
m
(N2H), (ii) the shift of
m(C@N) to lower fre-
The infrared spectrum of the sulphate complex 4 has bands at
1425 and 617 cmꢂ1 characteristic for the uncoordinated sulphate
group [37]. The IR spectrum of the VO(IV) complex display a band
m
m
m
m
at 980 cmꢂ1 assigned to the stretching frequency of the
[38].
m(V@O)
band at higher wave numbers, (vi) the absence of the thioamide
band (IV) [33] with the simultaneous appearance of new bands
in the 340–390, 422–467, and 487–530 cmꢂ1 regions due to
The characteristic bands of 1,10-phenanthroline [35] appear at
1491, 1430, 830, and 694 cmꢂ1 in the IR spectra of the ternary
complex 8, suggesting Phen coordination in this complex.
the
m(M–S), m(M–N) and m(M–O) vibrations, respectively [34]
(Chart 2).
The appearance of two characteristic bands in the ranges 1558–
3.3. Molar conductance data
1495 cmꢂ1 and 1435–1316 cmꢂ1 in case of complexes 3 and 10
was attributed to
m
asym.(COOꢂ) and
m
sym.(COOꢂ), respectively, indi-
The metal complexes discussed herein were dissolved in DMF
or DMSO and the molar conductivities of their solutions (10ꢂ3 M)
at room temperature were measured to establish the charge of
the metal complexes. The conductance data, reported in Table 2,
indicated that all the metal complexes, except [LVO
(H2O)]2 ꢀ (SO4) ꢀ H2O (4), have conductivity values in the range
characteristics for the non-electrolytic nature [39], suggesting that
cating the participation of the carboxylate oxygen in the complexes
formation. The mode of coordination of carboxylate group has of-
ten been deduced from the magnitude of the observed separation
between the
) between
200 cmꢂ1 (243 cmꢂ1) suggesting the coordination of carboxylate
m m
asym.(COOꢂ) and sym.(COOꢂ). The separation value
(D
m
asym.(COOꢂ) and msym. in complex 3 was more than

2010
N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
CH3
CH3
H
N
H
N
N
N
N
N
Y
S
S
O
O
O
M
M
Y
O
Cl
Cl
O
O
M
5
Complex LCuCl M = Cu, Y = Cl
S
3
Complex [LCo(OC(O)CH3)]·H2O M = Co, Y = CH3COO
Y
N
N
N
H
H3C
CH3
Complex 2 [L2Co2Cl2]2H2O M = Co, Y =none
Complex L2Cu2Cl2(H2O)2 M = Cu, Y = H2O
H
N
N
6
N
S
O
CH3
O
M
O
O
H
N
N
S
N
N
N
S
N
H
O
N
O
H3C
Cu
Cl
Complex 9 [L2Ni]·3H2O M = Ni
Complex 7 [L2Cu]·H2O M = Cu
N
CH3
H
N
N
N
Complex 8 [LCuCl(Phen)]·2H2O
S
O
O
Ni
O
O
H3C
H
N
N
N
10
Complex
LNi(OOCCH3)
C
O
(SO4) H2O
O
S
V
H2O
O
2
4
Complex : [LVO(H2O)]2·(SO4)H2O
Chart 2. The proposed structures of metal complexes.
these complexes are neutral. On the other hand, the conductivity
value of the complex 4 showed that it is electrolyte.
antiferromagnetic interaction between the adjacent metal ions in
this binuclear complex. However, the dark brown [LCo(Ac)] ꢀ H2O
complex is four-coordinate and has magnetic susceptibility 2.2
B.M. suggesting considerable distortion toward a planar arrange-
ment [41].
3.4. Electronic spectra and magnetic moments
3.4.1. Cobalt(II) complexes
The electronic spectrum for a square pyramidal d7 configuration
3.4.2. Copper(II) complexes
4
exhibits three transitions arising from the ground state A1g to
The magnetic moments of the copper complexes 7 and 8 at
room temperature lie in the range 1.72–1.89 B.M. given in Table
6, corresponding to one unpaired electron and fall within the range
observed for octahedral Cu(II) complexes [42]. This indicates that
these complexes are monomeric in nature and there are no me-
tal-metal interactions. The magnetic moment of complex 6 is 1.5
B.M., which is lower than the expected value for leff. of a single
Cu(II) ion in its octahedral complexes, thus it seems that there is
antiferromagnetic exchange existing between Cu(II) ions in this
complex. The electronic spectra of the copper complexes 6, 7 and
4
4
higher excited states B1g(m m2) and A2g(m3) [40]. As the m1
1), 4Eg(
band occurs at low energy, in the range not accessible due to
instrumental limitations, it was not observed in the spectrum of
complex 2. The band observed for this complex at 680 nm may
be due to the 4A1g ? 4Eg(
m
2) transition, corresponding to a square
pyramidal geometry. The highest band assigned to 4A1g ? 4Eg(m2
)
transition was not observed due to overlapping with the more in-
tense intraligand and charge transfer bands in the range 340–
440 nm. The magnetic moment of complex 2 is 3.07, and indicates

N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
2011
Table 4
The electronic absorption spectral bands (nm) and magnetic moment (B.M.) for the ligand HL and its complexes
No.
Ligand/complex
Mode
p
–
p* , n–p* and CT bands
d–d bands
680
leff in BM
1
2
HL
Nujol
Nujol
DMSO
Nujol
DMSO
Nujol
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
280, 342.5, 380, 487.5
270, 290, 350, 440
260, 300, 340
260, 280, 450
257, 300, 455
[L2Co2Cl2] ꢀ 2H2O
3.07
2.2
3
4
[LCo(OC(O)CH3)] ꢀ H2O
[LVOH2O]2 ꢀ H2O ꢀ (SO4)
270, 350, 460
265, 340, 470
660, 790
1.73
5
6
7
8
9
10
LCuCl
275, 297, 315, 455
260, 310, 425
260, 280, 330, 450
258, 290, 305, 417
275, 350, 460
730
680
620
610
840
520, 700
1.79
1.5
1.72
1.89
3.39
3.87
L2Cu2Cl2(H2O)2
[L2Cu] ꢀ H2O
[LCuCl(phen)] ꢀ 2H2O
[L2Ni] ꢀ 3H2O
LNi(OOCCH3)
290, 380, 460
Table 5
8
show bands in the range of 680–610 nm assignable to
ESR parameters for copper(II) complexes
2B1 g?2B2 g transition. This suggest that these complexes have
tetragonal distorted octahedral geometry [43,44].
The presence of an absorption band at 730 nm in complex 5, is
presumably due to d–d transition. The green colour of this chelate
confirms the distorted tetrahedral structure of this copper complex
[45].
No.
Complex
g//
g
(g//)/(A//)
G
gav.
5
6
7
8
LCuCl
2.24
1.99
2.2
2.04628
1.94
2.04
161
5.4
L2Cu2Cl2(H2O)2
[L2Cu] ꢀ H2O
0.20
5.24
4.49
1.96
2.1
2.0
214
194
[LCuCl(Phen)] ꢀ 2H2O
2.17
2.04
3.4.3. Nickel(II) complexes
the square planar geometry. The values of g///A// quotient in the
range (105–135 cm) are expected for copper complexes within
perfectly square based geometry and those higher than 150 cm
for tetrahedrally distorted complexes. The values for the com-
plexes under investigation, Table 5, showed that all complexes
are associated with a tetrahedrally distorted field around the cop-
per(II) centres.
[L2Ni] ꢀ 3H2O, (9) is high spin with a magnetic moment value of
3.39 B.M., which is in the normal range observed for octahedral
Ni(II) complexes. Its electronic spectrum displays a band at
840 nm which can be assigned to 3A2g ? 3T2g transition, consistent
with its octahedral stereochemistry [46].
LNi(OOCCH3), (10) shows recognizable bands at 700 and
520 nm. The positions of these spectral bands are consistent with
those predicted for five coordinate Ni(II) complex [46]. These
bands can be assigned respectively to 3B1 ? 3E and 3B1?3A2 tran-
sitions assuming the effective symmetry to be C4v [47].
3.6. Catalytic activity
The catalytic activity of complexes [L2Co2Cl2] ꢀ 2H2O (2),
[LCo(OC(O)CH3)] ꢀ H2O (3) and LCuIICl (5) in cyclopropanation reac-
tions has been investigated. As a model reaction we choose the
3.4.4. Vanadyl complex
The electronic spectrum of this complex has two bands in the
visible region at 790 and 520 nm, which are assigned to 2B2 ? 3E
and 2B2 ? 2B1 transitions, respectively, as expected for a square
pyramidal geometry in accordance with the Ballhausen–Gray
scheme [48]. This complex exhibits magnetic moment due to its
spin-only value of 1.73 B.M.
cyclopropanation of
a-methyl styrene by EDA (EDA = ethyl diazo-
acetate) (Scheme 3). Catalytic reactions were run by adding the
EDA to a stirred solution containing the olefin and the metal com-
plex in dichloroethane under dinitrogen.
Both cobalt complexes have a low catalytic activity as cyclo-
propanation catalyst and at 75 °C in 1,2-dichloroethane at a [Co]/
EDA/olefin ratio of 1:100:400 we observed a conversion of less
than 5% based on EDA after 2 h.
3.5. ESR Spectra
On the other hand, the copper complex LCuIICl (5), exhibited an
interesting catalytic capability toward the decomposition of ethyl
diazoacetate, and the subsequent transfer of the carbene moiety
to the C@C double bond. The condition of the catalytic reactions
have been examined by changing the temperature, and the relative
ratio [Cu]/EDA/olefin. Results are summarised in Table 6.
As it can be seen from data reported in Table 6, LCuIICl is a
very active catalyst for cyclopropanation reactions. A large excess
of the olefin is not required for the reaction to proceed: even if
equimolar amounts of EDA and olefin were used the cyclopropane
products were obtained in reasonable yields (60%); the rest of the
starting EDA is consumed to form the well-known coupling
The X-band ESR spectra of the polycrystalline samples of the
copper complexes are recorded at room temperature (298 K) and
the data are given in Table 5. The spectra of all complexes are of
axial shape with g// > g\ characteristic of complexes with
2B1(dx2-y2) orbital ground state. The average g values were calcu-
lated according to the equation gav = 1/3[g// + 2 g\] and the results
are given in Table 5. All complexes exhibit g// < 2.3, suggesting
covalent characters around the copper in present complexes. Kivel-
son and Neiman [49] have reported that a g// value greater than 2.3
indicates ionic character. The parameter G is calculated according
to the equation G = (g// ꢂ 2.0023)/(g\ ꢂ 2.0023) and shows values
>4. Data reported in Table 5, except in case of L2Cu2Cl2 ꢀ (H2O)2
complex (6), indicate that there is no direct copper-copper interac-
tion in the solid state. In case of complex 6, the G value is <4, which
suggests considerable exchange interaction in this solid complex.
The g///A// is taken as an indication for the stereochemistry of the
copper(II) complexes. Addison [50] has suggested that this ratio
may be an empirical indication of the tetrahedral distortion of
H3C
Ph
cat.
EDA, C2H4Cl2
+
H
H C
3 Ph
COOEt
Ph
COOEt
H
trans
cis
Scheme 3.

2012
N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
Table 6
(Table 7, entry 3). Even with these para substituted styrenes, the
catalytic cycle can be restored just by addition of both reactants.
In the second run and third run we observed even shorter reactions
Cyclopropanation of a
-methyl styrene with EDA catalysed by LCuIICl (5)a
Entry 5/EDA/olefin
T
(°C)
Time
(min)
Conversionb
(%)
Yieldc
(%)
cis:trans
times. It can be seen that in the absence of an
styrene derivative the formation of the trans cyclopropane is
slightly favored. Steric hindrance at the position does not hamper
a-substituent on the
1
2
3
1:100:100
1:100:200
60
75
R T
60
65
75
60
75
60
75
60
75
60
39
18
33
34
24/16/8
11
35
23
29
17
40
22
99
>99
>99
2
61.0
60.0
42:48
44:56
40:60
41:59
47:53
46:54
41:59
46:54
47:53
46:54
42:58
47:53
46:54
40:60
a
the reaction and good yields are obtained even with 1,1-diphenyl
ethylene (Table 7, entry 4). On the other hand, steric hindrance
at the b-position of the styrene greatly affected the reactivities.
Trans-b-methyl styrene gave lower reaction yields (55%) although
with a good diastereoselectivity (Table 7, entry 7), whilst with
cis-stilbene a dramatic drop in the cyclopropanation products
was observed (Table 7, entry 6).
Even aliphatic double bonds that are generally less reactive to-
wards cyclopropanation, gave excellent results. Though the time of
the cyclopropanation reaction for these substrates increased
slightly if compared to what observed for styrenic derivatives, very
good yields were always obtained (Table 7, entries 8–11). Even in
these cases trans cyclopropane compounds are obtained as major
products and a remarkable diastereoselectivity (trans/cis = 11.5)
has been observed in the case of cyclohexene (Table 7, entry 9).
With 2,5-dimethyl-2,4-hexadiene, an important precursor to chry-
santhemic acid [51], the catalytic reaction yielded the desired
cyclopropanes in very good yields (91%) and with reasonable dia-
stereoselectivities (Table 7, entry 10), without the need of a large
excess of the olefin.
4
>99
>99
>99
>99
>99
>99
>99
>99
>99
>99
77
72.2
72.7
66.5
82.6
84.6
72.0
66.8
86.8
75.8
77.8
60.1
5d
6
7
8
9
10
11
12
13
14e
1:100:2000
1:200:400
1:200:2000
1:1000:2000
1:12500:25000 60
360
a
Experimental conditions: EDA was added to a solution of LCuCl (5) (5.0 mg,
1.15 ꢁ 10ꢂ2 mmol) and
a-methyl styrene in dichloroethane (10 mL).
b
Conversion of the starting EDA.
Determined by GC–MS (yield based on EDA).
After complete consumption of the starting EDA, the catalytic cycle was
c
d
restored twice by addition of EDA and a-methyl styrene; global yield is reported.
e
LCuCl (5) (0.11 mg, 2.5 ꢁ 10ꢂ4 mmol) in dichloroethane (10 mL) were used. This
solution was prepared by dissolving L(Cu)Cl (5) (1.1 mg, 2.53 ꢁ 10ꢂ3 mmol) in
dichloroethane (100 mL).
Copper(I) complexes are known to be more efficient cycloprop-
anation catalysts than copper(II) compounds. It has been observed
that Cu(II) complexes are reduced to Cu(I) derivatives by the diazo
compound under the reaction conditions. This has led to general
agreement that the active catalyst is a Cu(I) species, irrespective
of the oxidation state of the copper complex used as the precata-
lyst. It is also generally accepted that transition metal-catalysed
cyclopropanation reactions proceed via a metal–carbene complex,
which is formed by association of the diazo compound and the
catalyst with concomitant extrusion of nitrogen [52]. Even if a de-
tailed mechanistic study of the cyclopropanation reaction cata-
lysed by complex LCuIICl (5) has not been undertaken yet,
however, preliminary 1H NMR experiments looking at the reac-
tion of complex LCuIICl (5) (2 mg, 4.59 ꢁ 10ꢂ3 mmol) with EDA
by-products (maleate and fumarate) normally obtained in cyclo-
propanation reactions (Table 6, entries 1 and 2). The temperature
plays an important role in these reactions: the catalyst at room
temperature is inactive (Table 6, entry 3), but as soon as the tem-
perature is increased to 60 °C it becomes very active. Reaction
times can be almost reduced to a half just by increasing the tem-
perature at 75 °C. After complete consumption of the starting
EDA, the catalytic cycle can be restored just by addition of both
reactants. In the second and third runs we observed even shorter
reactions times (see later). The cis:trans ratio is not affected to a
large extent by changing the conditions and nearly equal amounts
of both cyclopropanes have always been obtained. The best result
in terms of cyclopropane yield (86.8% based on EDA) was ob-
tained at 60 °C at a 5/EDA/olefin ratio of 1:200:2000 (Table 6, en-
try 11). In contrast to the prolonged EDA addition time generally
required to reduce the formation of coupling products in cyclo-
propanation, we found complex 5 to be very active: a loading of
0.1 mol% of the catalyst and one pot addition of EDA completely
consumed all the EDA and afforded cyclopropane products with
good selectivity (77.7% based on EDA) in less than 100 min
(TON 1000, Table 6, entry 13). The turnover number (TON)
reached 9625 at a 5/EDA/olefin ratio of 1:12550:25000 at 60 °C;
in this case we observed a 77% conversion of the starting EDA
in just 6 h (Table 6, entry 14).
in the presence of
a-methyl styrene, at a ratio [Cu]/EDA/olefin
of 1:5:10 in CDCl3 (1 mL), showed the formation of a diamagnetic
copper(I) complex during the reaction. Due to the very high reac-
tivity of this complex, any attempt to isolate it met with failure.
We can anyway note the following: (i) All the catalytic reactions
tested need an induction period before the nitrogen evolution due
to the EDA decomposition was observable. All the reactions were
also followed by IR spectroscopy monitoring the disappearance of
the band due to the stretching of the N2 moiety of the EDA
(m
= 2114 cmꢂ1). The consumption of the diazoacetate always
started after an induction period. This explains why the catalytic
cycle is faster in the second and third runs. This induction period
depends also on the concentration of the olefin and increases with
increasing the olefin concentration. (ii) When the EDA conversion
reached completion, it was possible to restore the catalytic cycle
just by adding new EDA and olefin to the reaction. In this case
no induction period was necessary to the system and the reac-
tions always proceeded to give cyclopropanes with almost identi-
cal yields. (iii) During the reaction the colour of the solution, due
to the dissolved copper complex, changed from green (due cop-
per(II) complex) to light yellow. The time needed for the change
in colour was always coincident with the induction period. (iv)
The induction period observed depends also on the olefin em-
ployed and longer times are observed for trans-b-methyl styrene
or non conjugated double bonds (see also Table 7). (v) If the reac-
tion is run in the air, longer reaction times are needed and we
Several alkenes were employed to determine the substrate
scope of the complex LCuIICl (5) as cyclopropanation catalyst. At
a 5/EDA/olefin ratio of 1:100:200 at 75 °C, the complex catalysed
the cyclopropanation of a range of substrates with quantitative
conversion in short reaction times and with selectivities ranging
from good to excellent. The results are summarised in Table 7.
When styrene is employed as substrate, we observed the quan-
titative conversion of the starting EDA in a comparable rate to what
observed in the case of a-methyl styrene (compare entry 1, Table 7
and entry 6, Table 6). However, in this case the diastereoselectivity
is improved (cis:trans = 33:67). Better yields in cyclopropane prod-
ucts, although with slightly longer reaction times, are obtained
when electron-donating substituents are present in the para posi-
tion of the aromatic ring (Table 7, entry 2). The same effect is ob-
served when employing 4-chloro-a-methylstyrene as substrate

N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
2013
Table 7
Cyclopropanation of olefins with EDA catalysed by LCuIICl (5)a
Entry
1
Olefin
Time (min)
12
Conversionb (%)
>99
Yieldc (%)
59
cis:transc
33:67
2d
3d
4
18/12/7
15/7/7
16
>99
>99
>99
87
87
68
34:66
49:51
Cl
Ph
5
6
7
24
15
19
>99
>99
>99
56
2.0
55
29:71
39:63
28:72
Ph
8
9
22
25
>99
>99
70
83
31:69
8:92
C6H13
10
21
18
>99
>99
91
84
35:65
11e
59:40:1
a
Experimental conditions: EDA was added to a solution of LCuCl (5) (5.0 mg, 1.15 ꢁ 10ꢂ2 mmol) and olefin in dichloroethane (10 mL) at 75 °C.
Conversion of the starting EDA.
Determined by GC–MS (yield based on EDA).
After complete consumption of the starting EDA, the catalytic cycle was restored twice by addition of EDA and olefin; global yield is reported.
Only three products out of four possible diastereoisomers were detected by GC–MS.
b
c
d
e
never obtained a full conversion of the starting EDA in these
cases.
All this data, together with the data reported in literature [53],
suggest that the catalyst is activated during the induction period
and that the initial reduction of copper(II) to copper(I) is necessary
to the catalysis to take place.
structures. The spectral data indicate that the ligand can behave
as monobasic tridentate ligand and coordinates through the C@N,
C@O and C–S groups with displacement of one hydrogen atom
upon enothiolization.
The monomeric copper(II) complex, LCuIICl, showed excellent
catalytic activity in cyclopropanation reaction and we have re-
ported that TON up to 9625 can be obtained. In contrast to the pro-
longed EDA addition time generally required to reduce the
formation of coupling products in cyclopropanation, we found this
complex to be very active and one pot addition of EDA is allowed to
yield the desired cyclopropanes with excellent selectivity. More-
over the catalyst is very robust and no decrease in yield was ob-
served even after three catalytic runs.
4. Conclusions
The straightforward synthesis of the new Schiff base, HL, 3-ace-
tylcoumarin-N(4)-phenylthiosemicarbazone has been reported. Its
metal complexes with transition metals have been characterised
and all the data collected are in agreement with the proposed

2014
N.S. Youssef et al. / Inorganica Chimica Acta 362 (2009) 2006–2014
[29] Z. Holzbecher, L. Divis, M. Kral, L. Sucha, F. Vlacil, Hand book of Organic
References
Reagents in Inorganic Analysis, John Wiley, New York, 1976.
[30] A.M.G. Macdonald, P. Sirichanya, Microchem. J. 14 (1969) 199.
[31] N.S. Youssef, Synth. React. Inorg. Met.-Org. Chem. 30 (2000) 225.
[32] V. Philip, V. Suni, M.R. Prathapachandra Kurup, M. Nethaji, Polyhedron 25
(2006) 1931.
[33] R.P. John, A. Sreekanth, M.R.P. Kurup, S.M. Mobin, Polyhedron 21 (2002) 2515.
[34] K.H. Reddy, P.S. Reddy, Transition Met. Chem. 25 (2000) 505.
[35] D.M. Boghaei, M. Gharagozlou, Spectrochim. Acta 67A (2007) 944.
[36] R.M. El-Shazly, G.A.A. Al-Hazmi, S.E. Ghazy, M.S. El-Shahawi, A.A. El-Asmy,
Spectrochim. Acta A61 (2005) 243.
[37] S. Chandra, L.K. Gupta, Spectrochim. Acta, Part A A61 (2005) 2549.
[38] A.A.A. Emara, A.A. Saleh, O.M.I. Adly, Spectrochim. Acta, Part A 68 (2007) 592.
[39] A. Golcu, M. Tumer, H. Demirelli, R.A. Wheatley, Inorg. Chim. Acta 358 (2005)
1785.
[40] S. Tascioglu, O. Buyukgungor, A. Aydin, A.K. Medjidov, Polyhedron 25 (2006)
1279.
[41] K.A. Ketcham, J.K. Swearingen, A. Castineiras, I. Garcia, E. Bermejo, D.X. West,
Polyhedron 20 (2001) 3265.
[42] G.G. Mohamed, N.E.A. El-Gamel, Spectrochim. Acta, Part A A60 (2004) 3141.
[43] S. Chandra, Sangeetika, Spectrochim. Acta, Part A 60 (2004) 2153.
[44] N.M. Shauib, A.-Z.A. Elassar, A. El-Dissouky, Spectrochim. Acta, Part A 63
(2006) 714.
[45] R.N. Jedeja, N.J. Parmar, Synth. React. Inorg. Met.-Org. Chem. 35 (2005) 111.
[46] S. Chandra, U. Kumar, Spectrochim. Acta, Part A 61 (2005) 219.
[47] G.G. Mohamed, Spectrochim. Acta, Part A 64 (2006) 188.
[48] U.B. Gangadharmath, S.M. Annigeri, A.D. Naik, V.K. Revankar, V.B. Mahale, J.
Mol. Struct. 572 (2001) 61.
[49] D. Kivelson, R. Neiman, J. Chem. Phys. 35 (1961) 149.
[50] A.W. Addison, in: K.D. Karlin, J. Zubieta (Eds.), Copper Coordination Chemistry
Biochemical and Inorganic Perspectives, Adenine Press, New York, 1983.
[51] M. Itagaki, K. Suenobu, Org. Process Res. Dev. 11 (2007) 509.
[52] J.M. Fraile, J.I. Garcia, V. Martinez-Merino, J.A. Mayoral, L. Salvatella, J. Am.
Chem. Soc. 123 (2001) 7616.
[1] F.D. Karia, P.H. Parsania, Asian J. Chem. Soc. 11 (1999) 991.
[2] P.G. More, R.B. Bhalvankar, S.C. Pattar, J. Indian Chem. Soc. 78 (2001) 474.
[3] A.H. El-Masry, H.H. Fahmy, S.H.A. Abdelwahed, Molecules 5 (2000) 1429.
[4] M.A. Baseer, V.D. Jadhav, R.M. Phule, Y.V. Archana, Y.B. Vibhute, Orient. J. Chem.
16 (2000) 553.
[5] S.B. Desai, P.B. Desai, K.R. Desai, Heterocycl. Commun. 7 (2001) 83.
[6] E.M. Hodnett, W.J. Dunn, J. Med. Chem. 13 (1970) 768.
[7] P. Pathak, V.S. Jolly, K.P. Sharma, Orient. J. Chem. 16 (2000) 161.
[8] S.N. Pandeya, D. Sriram, G. Nath, E.D. Clercq, Il Farmaco 54 (1999) 624.
[9] W.M. Singh, B.C. Dash, Pesticides 22 (1988) 33.
[10] S. Samadhiya, A. Halve, Orient. J.Chem. 17 (2001) 119.
[11] B.D. Clercq, F. Verpoort, Macromolecules 35 (2002) 8943.
[12] T. Opstal, F. Verpoort, Synlett 6 (2002) 935.
[13] T. Opstal, F. Verpoort, Angew. Chem., Int. Ed. 42 (2003) 2876.
[14] S.N. Pal, S. Pal, Inorg. Chem. 40 (2001) 4807.
[15] B.D. Clercq, F. Verpoort, Adv. Synth. Catal. 34 (2002) 639.
[16] B.D. Clercq, F. Lefebvre, F. Verpoort, Appl. Catal. A247 (2003) 345.
[17] Z. Li, G.L.Z. Zheng, H. Chen, Tetrahedron 56 (2000) 7187.
[18] L. Cai, H. Mahmoud, Y. Han, Tetrahedron: Asymmetry 10 (1999) 411.
[19] C.-M. Che, H.-L. Kwong, W.-C. Chu, K.-F. Cheng, W.-S. Lee, H.-S. Yu, C.-T. Yeung,
K.-K. Cheung, Eur. J. Inorg. Chem. (2002) 1456.
[20] H.B. Zhu, Z.Y. Dai, W. Hung, K. Cui, S.H. Gou, C.J. Zhu, Polyhedron 23 (2004)
1131.
[21] K.M. Gillespie, C.J. Sanders, P. O’Shaughnessy, I. Westmoreland, C.P. Thickitt, P.
Scott, J. Org. Chem. 67 (2002) 3450.
[22] T. Nagata, K. Yorozu, T. Yamada, T. Mukaiyama, Angew. Chem., Int. Ed. 34
(1995) 2145.
[23] E.N. Jacobsen, W. Zhang, M.L. Guler, J. Am. Chem. Soc. 113 (1991) 6703.
[24] G.L. Estiu, A.H. Jubert, J. Costamagna, J. Vargas, Inorg. Chem. 35 (1996) 263.
[25] H. Lebel, J.-F. Marcoux, C. Molinaro, A.B. Charette, Chem. Rev. 103 (2003) 977.
[26] H. Pellissier, Tetrahedron 64 (2008) 7041.
[27] F.J. Welcher, The Analytical Use Of EDTA, Van Norstrand, USA, 1958.
[28] A.I. Vogel, A Text Book of Quantitative Inorganic Analysis, fourth ed., Longman,
London, 1978.
[53] R.L. Safiullin, V.A. Dokichev, L.R. Yakupova, R.M. Sultanova, S.L. Khurasan, R.N.
Zaripov, Y.U.V. Tomilov, Kinet. Catal. 49 (2008) 43.